Shock absorber

Abstract

A shock absorber (D) is provided with: a cylinder (1); a piston (2) that is movably inserted into the cylinder (1) and partitions the inside of the cylinder (1) into an extension-side chamber (R1) and a compression-side chamber (R2) that are filled with a liquid; a piston rod (3) that is inserted into the cylinder (1) and that is connected to the piston (2); and an outer tube (4) that is disposed on the outer peripheral side of the cylinder (1) and in which a liquid storage chamber (R3) that is filled only with the liquid is formed. A damping passage (P) that connects the extension-side chamber (R1) and the reservoir chamber (R3); a variable damping valve (V) that is provided in the damping passage (P) and that can adjust resistance applied to the liquid flowing from the extension-side chamber (R1) to the reservoir chamber (R3); and a reservoir tank (6) that is disposed outside the outer tube (4), communicates with the reservoir chamber (R3), and stores the liquid.

Description

Technical Field

[0001] The present invention relates to a buffer. Background Art

[0002] For buffers that apply a damping force to suppress vibration, some can adjust the damping force. Among such buffers, for example, it is well known that there is a buffer that uses a solenoid-operated electromagnetic valve as a damping valve to adjust the damping force. Among them, if a damping valve that generates a damping force during the extension action and a damping valve that generates a damping force during the contraction action are provided in order to adjust the damping force in both the extension action and the contraction action, the cost is high at this time.

[0003] Therefore, a buffer having the following structure has been developed. It is provided with a damping passage through which hydraulic oil passes regardless of whether the buffer is extending or contracting, and a damping valve is provided on the damping passage, and the damping force in both the extension action and the contraction action can be adjusted.

[0004] Specifically, as shown in Japanese Patent JP2014-231912A, this buffer includes a cylinder, a piston that can be slidably inserted into the cylinder, a piston rod that can be movably inserted into the cylinder and is connected to the piston, a rod-side chamber and a piston-side chamber separated by the piston inserted into the cylinder, an intermediate cylinder that covers the outer periphery of the cylinder and forms a damping passage between it and the cylinder, and an outer tube that covers the outer periphery of the intermediate cylinder and forms a liquid storage chamber between it and the intermediate cylinder, a suction passage that only allows hydraulic oil to flow from the liquid storage chamber to the piston-side chamber, a piston passage provided on the piston that only allows hydraulic oil to flow from the piston-side chamber to the rod-side chamber, and a damping valve provided between the damping passage and the liquid storage chamber. Prior Art Documents Patent Documents

[0005] Patent Document 1: JP2014-231912A Summary of the Invention Problems to be Solved by the Invention

[0006] In the conventional buffer configured in this way, the hydraulic oil passing through the damping valve becomes a jet and rushes into the liquid storage chamber turbulently, and the hydraulic oil in the liquid storage chamber facing the gas is agitated by this jet. Once gas is entrained and mixed into the hydraulic oil in the liquid storage chamber, the waveform of the damping force (damping waveform) generated by the displacement of the buffer becomes disordered, making it difficult to achieve the target damping force.

[0007] Therefore, in conventional buffers, it is necessary to increase the amount of oil in the liquid storage chamber so that the oil level in the liquid storage chamber is as far as possible from the liquid outlet of the damping valve. As a result, the axial length of the outer tube forming the liquid storage chamber becomes longer, and thus the basic length of the buffer becomes longer. In this way, if the basic length of the buffer becomes longer, the mounting performance of the buffer on the installation object is reduced.

[0008] Therefore, an object of the present invention is to provide a buffer that can exhibit a target damping force without degrading its mounting performance on the installation object. Solution to the problem

[0009] To achieve the above object, the buffer of the present invention includes a cylinder, a piston that is freely movably inserted into the cylinder and divides the inside of the cylinder into an extension-side chamber filled with liquid and a compression-side chamber, a piston rod that is inserted into the cylinder and connected to the piston, an outer tube disposed on the outer peripheral side of the cylinder and forming a liquid storage chamber filled only with liquid inside, a damping passage that communicates the extension-side chamber with the liquid storage chamber, a variable damping valve provided on the damping passage and capable of adjusting the resistance applied to the liquid flowing from the extension-side chamber to the liquid storage chamber, and a liquid storage tank disposed outside the outer tube and communicating with the liquid storage chamber for storing liquid.

[0010] In the buffer configured in this way, since the liquid storage tank is provided outside the outer tube, the liquid storage chamber is filled only with liquid. When performing an extension operation or a contraction operation, even if the liquid flows into the liquid storage chamber through the variable damping valve, it is possible to prevent gas from being entrapped in the liquid in the liquid storage chamber. Description of the drawings

[0011] Figure 1 is a cross-sectional view of a buffer according to an embodiment. Figure 2 is a schematic diagram of the damping force characteristics of a buffer according to an embodiment. Figure 3 is a cross-sectional view of a buffer according to a modified example of an embodiment. Detailed description of the invention

[0012] Next, the buffer D of the present invention will be described with reference to the drawings. As Figure 1As shown, the buffer D in one embodiment is configured to include a cylinder 1, a piston 2 that is movably inserted into the cylinder 1 and divides the interior of the cylinder 1 into an extension side chamber R1 filled with liquid and a compression side chamber R2, a piston rod 3 that is inserted into the cylinder 1 and connected to the piston 2, an outer tube 4 disposed on the outer peripheral side of the cylinder 1 and having a liquid storage chamber R3 filled only with liquid formed therein, a damping passage P that communicates the extension side chamber R1 with the liquid storage chamber R3, a variable damping valve V provided on the damping passage P and capable of adjusting the resistance applied to the liquid flowing from the extension side chamber R1 to the liquid storage chamber R3, and a liquid storage tank 6 disposed outside the outer tube 4 and communicating with the liquid storage chamber R3 for storing liquid.

[0013] Next, each part of the buffer D will be described in detail. The cylinder 1 is cylindrical, and as described above, the piston 2 is movably inserted therein. Above the middle of the piston 2 Figure 1 divides the extension side chamber R1, and below the middle of Figure 1 divides the compression side chamber R2. In the extension side chamber R1 and the compression side chamber R2, specifically, hydraulic oil can be filled as the liquid. In addition, as the liquid, in addition to hydraulic oil, water, aqueous solution, etc. can also be filled.

[0014] In addition, the cylinder 1 is accommodated in a bottomed cylindrical outer tube 4 disposed on the outer peripheral side. In addition, an intermediate tube 7 is inserted between the cylinder 1 and the outer tube 4, and the damping passage P is formed by the annular gap between the cylinder 1 and the intermediate tube 7, and the liquid storage chamber R3 is formed by the annular gap between the intermediate tube 7 and the outer tube 4. In addition, a hole 1a communicating the extension side chamber R1 and the damping passage P is provided near the upper end of the cylinder 1. Further, the outer tube 4 covers the outer periphery of the cylinder 1 over the entire length of the cylinder 1 and accommodates the entire cylinder 1 therein. Similar to the cylinder 1, the interior of the damping passage P and the interior of the liquid storage chamber R3 are filled with hydraulic oil.

[0015] Moreover, a valve housing 8 is fitted to the lower ends of the cylinder 1 and the intermediate tube 7 Figure 1 , and a guide member 9 for slidably and axially supporting the piston rod 3 is fitted to the upper ends of the cylinder 1 and the intermediate tube 7 Figure 1 . The cylinder 1 and the intermediate tube 7 are clamped by the valve housing 8 and the guide member 9 and positioned concentrically in the radial direction. In addition, the lower ends of the cylinder 1 and the intermediate tube 7 are both closed by the valve housing 8, and the compression side chamber R2 inside the cylinder 1 and the liquid storage chamber R3 formed outside the cylinder 1 and inside the outer tube 4 are separated by the valve housing 8.

[0016] The valve housing 8 and the guide 9 that hold the cylinder 1 and the intermediate cylinder 7 in this manner are both inserted into the inner circumference of the outer tube 4. Further, if the upper end of the outer tube 4 is caulked, the cylinder 1, the intermediate cylinder 7, the valve housing 8, and the guide 9 are clamped and fixed within the outer tube 4 by the caulked portion and the bottom of the outer tube 4. Sealing members (not shown) are provided between the guide 9 and the piston rod 3 and between the guide 9 and the outer tube 4 to prevent leakage of the liquid within the shock absorber D. Further, instead of caulking the upper end opening of the outer tube 4, a lid may be screwed onto the upper end opening of the outer tube 4, and the guide 9, the cylinder 1, the intermediate cylinder 7, and the valve housing 8 may be clamped by this lid and the bottom of the outer tube 4 to fix these components within the outer tube 4.

[0017] The piston 2 is annular and connected to the piston rod 3, dividing the interior of the cylinder 1 into, as Figure 1 the upper elongation side chamber R1 above, and Figure 1 the lower compression side chamber R2 below, and includes an elongation side port 2a that communicates the elongation side chamber R1 and the compression side chamber R2, and a compression side port 2b that communicates the compression side chamber R2 and the elongation side chamber R1.

[0018] Further, on the Figure 1 upper side of the piston 2, i.e., on the elongation side chamber side, a compression side check valve 12 formed by laminating a plurality of annular plates is provided. The inner circumference of the compression side check valve 12 is fixed to the outer circumference of the piston rod 3 and allows bending on the outer peripheral side. When the pressure within the compression side chamber R2 is higher than the pressure within the elongation side chamber R1 and the compression side check valve 12 bends under the pressure applied from the compression side chamber R2 through the compression side port 2b, the compression side port 2b is opened to communicate the compression side chamber R2 and the elongation side chamber R1, allowing hydraulic oil to flow from the compression side chamber R2 to the elongation side chamber R1.

[0019] Conversely, when the pressure within the elongation side chamber R1 is higher than the pressure within the compression side chamber R2, the compression side check valve 12 is pushed by the pressure of the elongation side chamber R1 acting from the back to close the compression side port 2b, thereby cutting off the communication between the compression side chamber R2 and the elongation side chamber R1. Further, the compression side check valve 12 can apply resistance to the flowing hydraulic oil in a state where the compression side port 2b is open, but does not cause a negative pressure within the elongation side chamber R1.

[0020] On the other hand, on the Figure 1On the lower side thereof, i.e., on the compression-side chamber side, an extension-side damping valve 13 composed of a plurality of annular plates stacked is provided. The inner circumference of the extension-side damping valve 13 is fixed to the outer circumference of the piston rod 3, allowing the outer circumference side to bend, thereby providing an initial bend. In addition, throttle holes 13a formed by cuts are provided on the outer circumference of the annular plate that can be detachably seated on the piston 2 of the extension-side damping valve 13. Even if the pressure in the extension-side chamber R1 is higher than the pressure in the compression-side chamber R2, the extension-side damping valve 13 will remain in the state of being seated on the piston 2 until the pressure difference between the extension-side chamber R1 and the compression-side chamber R2 reaches the opening pressure set by the initial bend. Therefore, in this state, the hydraulic oil only moves from the extension-side chamber R1 to the compression-side chamber R2 through the throttle holes 13a, and the throttle holes 13a apply resistance to the hydraulic oil. In addition, if the pressure in the extension-side chamber R1 is higher than the pressure in the compression-side chamber R2, and the pressure difference between the extension-side chamber R1 and the compression-side chamber R2 reaches the opening pressure, the extension-side damping valve 13 is bent by the pressure acting on the extension-side port 2a of the extension-side chamber R1, opening the extension-side port 2a, communicating the extension-side chamber R1 and the compression-side chamber R2, allowing the hydraulic oil to flow from the extension-side chamber R1 to the compression-side chamber R2, and applying resistance to the hydraulic oil. Conversely, if the pressure in the compression-side chamber R2 is higher than the pressure in the extension-side chamber R1, the extension-side damping valve 13 is pushed by the pressure of the compression-side chamber R2 acting from the back, closing the extension-side port 2a, and only allowing the extension-side chamber R1 and the compression-side chamber R2 to communicate through the throttle holes 13a.

[0021] Next, as Figure 1 shown, the valve housing 8 is annular and is configured to have a small-diameter portion 8a with a smaller diameter that fits into the lower end of the cylinder 1, and in the Figure 1 lower middle part of the small-diameter portion 8a and having an outer diameter larger than that of the small-diameter portion 8a, a middle-diameter portion 8b that fits into the lower end of the intermediate cylinder 7, a ring-shaped skirt portion 8c below the middle-diameter portion 8b and having an outer diameter larger than that of the middle-diameter portion 8b, a cut 8d provided in the skirt portion 8c and communicating the inside and outside of the skirt portion 8c, and from the upper end of the Figure 1 inside, i.e., the compression-side chamber end, leading to a damping port 8e and a suction port 8f facing the opposite end to the compression-side chamber inside the skirt portion 8c.

[0022] Moreover, the valve housing 8 fits the small-diameter portion 8a at the lower end of the cylinder 1 and Figure 1 at the lower end of the intermediate cylinder 7 Figure 1The lower end fitting middle diameter part 8b in it abuts the lower end of the skirt 8c against the bottom of the outer tube 4, and is clamped and fixed to the outer tube 4 by the outer tube 4 and the cylinder 1. The inside of the skirt 8c communicates with the liquid storage chamber R3 via the cutout 8d, and communicates with the compression side chamber R2 through the damping port 8e and the suction port 8f. Therefore, the compression side chamber R2 and the liquid storage chamber R3 communicate with each other through the cutout 8d, the inside of the skirt 8c, the damping port 8e and the suction port 8f.

[0023] On the upper side of the valve housing 8, Figure 1 an elongation side check valve 14 formed by laminating a plurality of annular plates is provided on the compression side chamber side, i.e., the upper side in it. The inner periphery of the elongation side check valve 14 is fixed to the outer periphery of the center rod 15 inserted through the inner periphery of the valve housing 8, and allows the outer periphery side to bend. When the pressure in the liquid storage chamber R3 is higher than the pressure in the compression side chamber R2 and the elongation side check valve 14 bends under the pressure acting on the suction port 8f from the liquid storage chamber R3, the suction port 8f is opened, and hydraulic oil is allowed to flow from the liquid storage chamber R3 to the compression side chamber R2. Conversely, when the pressure in the compression side chamber R2 is higher than the pressure in the liquid storage chamber R3, the elongation side check valve 14 is pushed by the pressure of the compression side chamber R2 acting from the back to close the suction port 8f, thereby cutting off the communication between the compression side chamber R2 and the liquid storage chamber R3. The elongation side check valve 14 can apply resistance to the passing hydraulic oil in the state where the suction port 8f is open, but will not make the inside of the cylinder 1 negative pressure.

[0024] On the other hand, in the valve housing 8, Figure 1On the lower side thereof, i.e., on the side opposite to the compression-side chamber, a compression-side damping valve 16 composed of a plurality of annular plates stacked is provided. The inner periphery of the compression-side damping valve 16 is fixed to the outer periphery of the center rod 15, allowing the outer peripheral side to bend, thereby providing an initial bend. In addition, a throttle hole 16a formed by a cut is provided on the outer periphery of the annular plate that can be detachably seated on the valve housing 8 of the compression-side damping valve 16. Even if the pressure in the compression-side chamber R2 is higher than the pressure in the liquid storage chamber R3, the compression-side damping valve 16 will remain seated on the valve housing 8 until the pressure difference between the pressure in the compression-side chamber R2 and the pressure in the liquid storage chamber R3 reaches the opening pressure set by the initial bend. Therefore, in this state, the hydraulic oil only moves from the compression-side chamber R2 to the liquid storage chamber R3 through the throttle hole 16a, and the throttle hole 16a applies resistance to the hydraulic oil. In addition, if the pressure in the compression-side chamber R2 is higher than the pressure in the liquid storage chamber R3 and the pressure difference between the pressure in the compression-side chamber R2 and the pressure in the liquid storage chamber R3 reaches the opening pressure, the compression-side damping valve 16 is bent by the pressure acting through the damping port 8e of the compression-side chamber R2, opening the damping port 8e, connecting the compression-side chamber R2 and the liquid storage chamber R3, allowing the hydraulic oil to flow from the compression-side chamber R2 to the liquid storage chamber R3, and applying resistance to the hydraulic oil. Conversely, if the pressure in the liquid storage chamber R3 is higher than the pressure in the compression-side chamber R2, the compression-side damping valve 16 is pushed by the pressure of the liquid storage chamber R3 acting from the back to close the damping port 8e, and only allows the compression-side chamber R2 and the liquid storage chamber R3 to be connected through the throttle hole 16a.

[0025] As described above, the intermediate cylinder 7 covers the outer periphery of the cylinder 1 and is clamped between the guide member 9 and the valve housing 8, forming an annular damping passage P therebetween. The damping passage P is connected to the extension-side chamber R1 through the hole 1a provided in the cylinder 1, and is connected to the liquid storage chamber R3 through the variable damping valve V. The intermediate cylinder 7 separates the cylinder 1 and the outer tube 4, forming an annular liquid storage chamber R3 therebetween.

[0026] The intermediate cylinder 7 has a hole 7a located below and a sleeve 7b that surrounds the hole 7a on the outer periphery and protrudes radially. Moreover, a valve housing 17 is fitted inside the sleeve 7b, and the variable damping valve V is provided inside the valve housing. The space between the sleeve 7b and the valve housing 17 is sealed by a sealing member (not shown) to prevent the damping passage P and the liquid storage chamber R3 from communicating through the space between the valve housing 17 and the sleeve 7b. In addition, although the hole 1a provided in the cylinder 1 is used to connect the damping passage P in the intermediate cylinder 7 and the extension-side chamber R1, a passage that connects the annular gap between the extension-side chamber R1 and the cylinder 1 and the intermediate cylinder 7 can also be provided on the guide member 9 instead of the hole 1a to connect the damping passage P and the extension-side chamber R1.

[0027] In addition, the outer tube 4 is provided with a hole 4a disposed at a position radially opposite to the hole 7a and the sleeve 7b of the intermediate cylinder 7, and a valve mounting cylinder 4b that surrounds the hole 4a on the outer periphery and protrudes radially. Moreover, the valve housing 17 is fitted into the valve mounting cylinder 4b, and the opening of the valve mounting cylinder 4b is closed by a bottomed cylindrical cover 19 screwed onto the outer periphery of the valve mounting cylinder 4b. In addition, a sealing member (not shown) is provided between the valve housing 17 and the valve mounting cylinder 4b to prevent the hydraulic oil in the liquid storage chamber R3 from leaking out of the outer tube 4 between the valve housing 17 and the valve mounting cylinder 4b.

[0028] The front end of the valve housing 17 is inserted into the sleeve 7b of the intermediate cylinder 7, and the rear end is inserted into the valve mounting cylinder 4b of the outer tube 4, with the front end facing the damping passage P and the side facing the liquid storage chamber R3. Moreover, the valve housing 17 is provided with a flow passage 18 that opens at the front end and communicates laterally to connect the damping passage P in the intermediate cylinder 7 and the liquid storage chamber R3 in the outer tube 4, and a variable damping valve V provided in the middle of the flow passage 18. The flow passage 18 of the valve housing 17 connects the annular gap to the liquid storage chamber R3, and together with the annular gap forms the damping passage P, where the annular gap is formed between the intermediate cylinder 7 and the outer tube 4 and communicates with the extension side chamber R1. Therefore, the variable damping valve V is provided in the middle of the damping passage P.

[0029] The variable damping valve V only allows the hydraulic oil to flow from the extension side chamber R1 to the liquid storage chamber R3 through the damping passage P, and applies resistance to the hydraulic oil passing through the damping passage P. More specifically, the variable damping valve V is an electromagnetic valve equipped with a solenoid, which applies resistance to the hydraulic oil flowing from the extension side chamber R1 through the damping passage P to the liquid storage chamber R3, and can adjust the opening pressure by the current applied to the solenoid. The variable damping valve V configured in this way can be used as a pressure control valve, and can adjust the opening pressure according to the amount of electricity supplied to the solenoid, thereby adjusting the damping force generated by the buffer. In addition, in addition to the damping valve that makes the damping force variable by adjusting the opening pressure, the variable damping valve V can also use a damping valve with any structure as long as the damping force can be adjusted.

[0030] Next, the liquid storage tank 6 is disposed outside the outer tube 4, and it includes a cylindrical container 6a and a free piston 6b that is movably inserted into the container 6a and divides the inside of the container 6a into a liquid chamber L filled with hydraulic oil and a gas chamber G filled with enclosed gas. Gas is enclosed in the gas chamber G in a compressed state, and the inside of the liquid chamber L of the liquid storage tank 6 is pressurized by the pressure in the gas chamber G. In addition, the liquid chamber L of the liquid storage tank 6 and the liquid storage chamber R3 in the outer tube 4 are connected to each other through a pipe 5, and the hydraulic oil can flow back and forth between the liquid chamber L and the liquid storage chamber R3.

[0031] The pipe 5 is formed of a flexible hose, one end of which is connected to the lower end of the container 6a, and the other end is connected to a position on the outer periphery of the outer pipe 4 that does not interfere with the valve housing 17. In addition to the flexible hose, the pipe 5 may also be formed of a material without flexibility such as a steel pipe. Further, although the liquid chamber L and the gas chamber G of the liquid storage tank 6 are separated by the free piston 6b, they may also be separated by a separating member such as an airbag, a diaphragm, or a bellows. These members can separate the liquid chamber L and the gas chamber G and change the volume distribution of the liquid chamber L and the gas chamber G in the container 6a. Additionally, for example, the connection portion of the pipe 5 of the container 6a may be arranged below or the like. As long as the gas can be prevented from moving from the container 6a of the liquid storage tank 6 to the liquid storage chamber R3, the separating member that separates the liquid chamber L and the gas chamber G may be omitted. Further, a structure may be adopted in which one end of the container 6a is open to the atmosphere and a spring is accommodated in the container 6a, and the spring applies a force to the free piston 6b in the direction of pressurizing the liquid chamber L. At this time, the gas chamber G filled with gas may not be provided in the container 6a.

[0032] In addition, since the other end of the pipe 5 may be connected to a position on the side portion of the outer pipe 4 that is far from the valve housing 17 and does not interfere with it, it may be connected to any position within the entire axial length range of the outer pipe 4. Additionally, the other end of the pipe 5 may be connected to the guide member 9, and a passage that communicates the inside of the pipe 5 and the liquid storage chamber R3 may be provided on the guide member 9.

[0033] Next, the operation of the buffer D configured in the above manner will be described. First, the case where the buffer D extends will be described. When the piston 2 moves upward in the cylinder 1 and the buffer D is in the extension stroke, the extension side chamber R1 is compressed and the compression side chamber R2 expands. When the moving speed of the piston 2 relative to the cylinder 1, that is, the piston speed, is low, the pressure in the extension side chamber R1 is higher than the pressure in the compression side chamber R2, but the differential pressure between the two does not reach the opening pressure of the extension side damping valve 13. Therefore, since the extension side damping valve 13 maintains the closed valve state, the hydraulic oil moves from the extension side chamber R1 to the compression side chamber R2 through the throttle hole 13a. Figure 1 Among them, if the opening pressure of the variable damping valve V is made lower than the opening pressure of the extension side damping valve 13, the variable damping valve V can open at a piston speed lower than the piston speed at which the extension side damping valve 13 opens. Therefore, in addition to the throttle hole 13a, the hydraulic oil also moves from the extension side chamber R1 to the liquid storage chamber R3 through the damping passage P. Additionally, if the opening pressure of the variable damping valve V is made higher than the opening pressure of the extension side damping valve 13, since the variable damping valve V maintains the closed valve state, the hydraulic oil only moves from the extension side chamber R1 to the compression side chamber R2 through the throttle hole 13a.

[0034]

[0035] Therefore, when in the extending stroke and the piston speed is in the low-speed range, as Figure 2 shown, the shock absorber D can, through the adjustment of the variable damping valve V, adjust the damping force within the range from the damping force when the opening pressure of the variable damping valve V is set to the minimum ( Figure 2 single dotted line in) to the damping force generated only by the throttle hole 13a ( Figure 2 solid line in).

[0036] In addition, during the extending stroke of the shock absorber D, since the piston rod 3 withdraws from the cylinder 1, the volume of hydraulic oil corresponding to the volume withdrawn by the piston rod 3 from the cylinder 1 is insufficient in the cylinder 1. The insufficient volume of hydraulic oil in the cylinder 1 is supplied into the cylinder 1 from the liquid chamber L of the liquid storage tank 6 through the liquid storage chamber R3 and the pipeline 5 due to the opening of the extension-side check valve 14. In the liquid storage tank 6, since the hydraulic oil is discharged from the liquid chamber L, the free piston 6b can move within the container 6a, on the one hand reducing the volume of the liquid chamber L and on the other hand expanding the volume of the gas chamber G. Thus, when the shock absorber D is in the extending stroke, hydraulic oil is supplied from the liquid storage tank 6 into the cylinder 1 to compensate for the volume withdrawn by the piston rod 3 from the inside of the cylinder 1.

[0037] In addition, when the piston speed during the extending stroke is high, the differential pressure between the extension-side chamber R1 and the compression-side chamber R2 becomes large. Before the differential pressure between the extension-side chamber R1 and the compression-side chamber R2 reaches the opening pressure of the extension-side damping valve 13, the pressure in the extension-side chamber R1 can be controlled by adjusting the opening pressure of the variable damping valve V. When the differential pressure between the extension-side chamber R1 and the compression-side chamber R2 reaches the opening pressure of the extension-side damping valve 13, the extension-side damping valve 13 opens, thereby opening the extension-side port 2a. Then, the hydraulic oil moves from the extension-side chamber R1 to the compression-side chamber R2 through the annular gap that appears between the extension-side damping valve 13 and the piston 2.

[0038] Therefore, when in the extending stroke and the piston speed is in the high-speed range, as Figure 2 shown, the shock absorber D can, through the adjustment of the variable damping valve V, adjust the damping force within the range between the damping force when the opening pressure of the variable damping valve V is set to the minimum ( Figure 2 single dotted line in) and the damping force generated by the extension-side damping valve 13 ( Figure 2 solid line in).

[0039] In addition, when in the extended stroke and with the variable damping valve V open, hydraulic oil flows from the extension side chamber R1 to the reservoir chamber R3 through the damping passage P and the variable damping valve V. However, only the reservoir chamber R3 is filled with hydraulic oil, and the hydraulic oil with a relatively high flow rate passing through the variable damping valve V is not in contact with the gas in the reservoir chamber R3 at all. Therefore, entrainment of gas can be prevented. In the shock absorber D of the present embodiment, since the interior of the container 6a of the reservoir 6 is separated into a liquid chamber L and a gas chamber G by a free piston 6b, even if the hydraulic oil is in the reservoir 6, it will not come into direct contact with the gas. Therefore, there is no problem even if the hydraulic oil flows into the reservoir 6. However, even if the free piston 6b and other separating components for separating the gas and the hydraulic oil are removed, even if the hydraulic oil passing through the variable damping valve V flows into the liquid chamber L in the reservoir 6, its flow can be made gentle when flowing through the pipe 5, thereby preventing the entrainment of gas in the hydraulic oil in the reservoir 6.

[0040] Next, the case where the shock absorber D contracts will be described. When the piston 2 moves downward in the cylinder 1 and the shock absorber D is in the contraction stroke, the compression side chamber R2 is compressed while the extension side chamber R1 expands. When the piston speed is low, the pressure in the compression side chamber R2 is higher than the pressure in the extension side chamber R1. Then, the compression side check valve 12 opens, and the hydraulic oil moves from the compression side chamber R2 to the extension side chamber R1. Figure 1 In addition, during the contraction stroke of the shock absorber D, since the piston rod 3 enters the cylinder 1, the hydraulic oil corresponding to the volume of the piston rod 3 entering the cylinder 1 becomes excessive in the cylinder 1. When the piston speed is low, due to the small differential pressure between the compression side chamber R2 and the reservoir chamber R3, the compression side damping valve 16 maintains the closed state. Therefore, the hydraulic oil moves from the compression side chamber R2 to the reservoir chamber R3 through the throttle hole 16a.

[0041] Among them, if the opening pressure of the variable damping valve V is set lower than the opening pressure of the compression side damping valve 16, the variable damping valve V can open at a piston speed lower than the piston speed at which the compression side damping valve 16 opens. Therefore, in addition to the throttle hole 16a, the hydraulic oil also moves from the inside of the cylinder 1 to the reservoir chamber R3 through the damping passage P. Additionally, if the opening pressure of the variable damping valve V is set higher than the opening pressure of the compression side damping valve 16, since the variable damping valve V maintains the closed state, the hydraulic oil only moves from the compression side chamber R2 to the reservoir chamber R3 through the throttle hole 16a.

[0042] Therefore, when in the contraction stroke and the piston speed is within the low-speed range, as

[0043] shown, by adjusting the variable damping valve V, the shock absorber D can achieve the damping force when the opening pressure of the variable damping valve V is set to the minimum ( Figure 2 Figure 2 ​is adjusted within a range between the damping force generated only by the throttle hole 16a (single dotted line in Figure 2 ) and the damping force generated only by the throttle hole 16a (solid line in

[0044] When the piston speed during the contraction stroke is high, the differential pressure between the compression side chamber R2 and the reservoir chamber R3 increases. Further, if the differential pressure between the compression side chamber R2 and the reservoir chamber R3 reaches the opening pressure of the compression side damper valve 16, the compression side damper valve 16 opens the damping port 8e. Before the differential pressure between the compression side chamber R2 and the reservoir chamber R3 reaches the opening pressure of the compression side damper valve 16, the pressure within the cylinder 1 can be controlled by adjusting the opening pressure of the variable damper valve V.

[0045] Therefore, when in the contraction stroke and the piston speed is within the high speed range, as Figure 2 shown, the shock absorber D can adjust the damping force within a range between the damping force when the opening pressure of the variable damper valve V is set to the minimum (single dotted line in Figure 2 ) and the damping force generated by the compression side damper valve 16 (solid line in Figure 2 ).

[0046] Further, when in the contraction stroke and the variable damper valve V is open, the hydraulic oil flows from the extension side chamber R1 to the reservoir chamber R3 through the damping passage P and the variable damper valve V. However, the reservoir chamber R3 is filled only with the hydraulic oil, and the hydraulic oil flowing at a relatively high speed through the variable damper valve V does not come into contact with the gas within the reservoir chamber R3 at all. Therefore, entrainment of gas can be prevented. Further, in the shock absorber D of the present embodiment, since the interior of the container 6a of the reservoir 6 is partitioned by the free piston 6b into the liquid chamber L and the gas chamber G, even if the hydraulic oil flows into the reservoir 6, the hydraulic oil will not come into direct contact with the gas. Therefore, there is no problem even if the hydraulic oil flows into the reservoir 6. However, even if the free piston 6b and other partitioning members for separating the gas and the hydraulic oil are removed, even if the hydraulic oil passing through the variable damper valve V flows toward the liquid chamber L within the reservoir 6, the flow of the hydraulic oil can be made gentle when passing through the pipe 5, and thus entrainment of gas in the hydraulic oil within the reservoir 6 can be prevented.

[0047] As can be understood from the above, the shock absorber D basically behaves as a single flow type shock absorber, and the hydraulic oil flows from inside the cylinder 1 through the variable damper valve V to the reservoir chamber R3 both during extension and during contraction. Further, when the pressure within the extension side chamber R1 is excessive, the extension side damper valve 13 can act as a flapper valve to move the hydraulic oil from the extension side chamber R1 to the compression side chamber R2, and when the pressure within the compression side chamber R2 is excessive, the compression side damper valve 16 can act as a flapper valve to move the hydraulic oil from the compression side chamber R2 to the reservoir chamber R3.

[0048] As described above, the buffer D includes a cylinder 1, a piston 2 that is movably inserted into the cylinder 1 and divides the interior of the cylinder 1 into an extension-side chamber R1 filled with hydraulic oil (liquid) and a compression-side chamber R2, a piston rod 3 that is inserted into the cylinder 1 and connected to the piston 2, an outer tube 4 disposed on the outer peripheral side of the cylinder 1 and forming a liquid storage chamber R3 filled only with hydraulic oil (liquid) inside, a damping passage P that communicates the extension-side chamber R1 with the liquid storage chamber R3, a variable damping valve V provided on the damping passage P and capable of adjusting the resistance applied to the hydraulic oil (liquid) flowing from the extension-side chamber R1 to the liquid storage chamber R3, and a liquid storage tank 6 disposed outside the outer tube 4 and communicating with the liquid storage chamber R3 through a pipe 5 for storing hydraulic oil (liquid).

[0049] In the buffer D configured in this way, since the liquid storage tank 6 is provided outside the outer tube 4, only hydraulic oil (liquid) can fill the liquid storage chamber R3. When performing an extension action or a contraction action, even if the hydraulic oil (liquid) flows into the liquid storage chamber R3 through the variable damping valve V, it is possible to prevent gas from being entrained in the hydraulic oil (liquid) in the liquid storage chamber R3. In addition, even if the interior of the liquid storage tank 6 is not partitioned into gas and liquid by a partitioning member, since the liquid storage chamber R3 communicates with the liquid storage tank 6 through the pipe 5, the flow rate of the hydraulic oil (liquid) is slowed down, and it is also possible to prevent gas from being entrained in the hydraulic oil (liquid) in the liquid storage tank 6.

[0050] Therefore, in the buffer D according to the present embodiment, since there is no need to worry about gas being entrained in the liquid storage chamber R3, the overall length of the outer tube 4 can be shortened. Not only can the basic length of the buffer D be shortened without impairing its mounting performance on the installation object, but also gas can be prevented from being entrained in the hydraulic oil (liquid), so that gas can be prevented from mixing into the cylinder 1, and thus the expected damping force can be exerted.

[0051] In addition, in the buffer D of the present embodiment, since only hydraulic oil (liquid) is filled in the liquid storage chamber R3 in the outer tube 4, the buffer main body including the cylinder 1, the piston 2, the piston rod 3, and the outer tube 4 can be arranged in an inverted manner with the cylinder 1 on the upper side and the piston rod 3 on the lower side or in a horizontal manner, and the buffer main body can be set according to the specifications of the installation position of the buffer D. Therefore, this also improves the mounting performance of the buffer D.

[0052] In addition, in the buffer D of the present embodiment, the liquid storage chamber R3 is filled only with hydraulic oil (liquid). Therefore, no matter where the variable damping valve V is set on the outer tube 4, it is possible to prevent gas from being entrapped in the hydraulic oil (liquid). Therefore, according to the buffer D of the present embodiment, the setting position of the variable damping valve V on the outer tube 4 can be freely set, so that the design freedom of the buffer D is improved. In addition, the variable damping valve V can be provided not only on the outer tube 4 but also on the guide member 9 or the valve housing 8.

[0053] Furthermore, in the buffer D of the present embodiment, the outer tube 4 covers the cylinder 1 over the entire axial length. According to the buffer D configured in this way, since the outer tube 4 covers the entire length of the cylinder 1, the setting position of the variable damping valve V on the outer tube 4 can be set at any position within the entire axial length range of the outer tube 4, and the design freedom of the setting position of the variable damping valve V is improved.

[0054] In addition, in the buffer D of the present embodiment, an intermediate cylinder 7 is provided between the cylinder 1 and the outer tube 4 and a damping passage P is formed between it and the cylinder 1, and a liquid storage chamber R3 is formed between the intermediate cylinder 7 and the outer tube 4. According to the buffer D configured in this way, by providing the intermediate cylinder 7 between the cylinder 1 and the outer tube 4, it is possible to easily form the damping passage P and the liquid storage chamber R3 with a simple structure. Therefore, it is possible to reduce the manufacturing cost while simplifying the assembly operation. In addition, when forming the damping passage P, it is also possible to design to cancel the intermediate cylinder 7 and provide a pipeline with one end mounted on the guide member 9 and housed between the cylinder 1 and the outer tube 4. The inside of the pipeline is communicated with the extension side chamber R1 through a passage provided on the guide member 9, and the other end of the pipeline is communicated with the liquid storage chamber R3 formed by the annular gap between the cylinder 1 and the outer tube 4, and the damping passage P is formed by this pipeline. It is only necessary to provide the variable damping valve V in the middle of the pipeline.

[0055] Furthermore, it is also possible to design to cancel the intermediate cylinder 7 and communicate the extension side chamber R1 with the liquid storage chamber R3 formed by the annular gap between the cylinder 1 and the outer tube 4 through a passage provided on the guide member 9, and provide the variable damping valve V on the guide member 9. In this case, since the intermediate cylinder 7 or the pipeline is not required, the number of components of the buffer D can be reduced.

[0056] In addition, in the buffer D of the present embodiment, the outer tube 4 covers the cylinder 1 and the intermediate cylinder 7 over the entire axial length, but it is also possible to form a liquid storage chamber R3 in the outer tube 4 to prevent gas from being entrapped in the hydraulic oil (liquid), and the axial length of the outer tube 4 can also be shorter than that of the cylinder 1 and the intermediate cylinder 7, provided that the variable damping valve V can be accommodated within the entire axial length range of the outer tube 4.

[0057] In addition, if the connection position of the pipe 5 on the outer pipe 4 or the guide member 9 is set at a position separated from the installation position of the variable damping valve V in the circumferential and vertical directions, it is possible to prevent the hydraulic oil with a relatively high flow rate flowing from the inside of the cylinder 1 into the liquid storage chamber R3 through the variable damping valve V from flowing into the liquid storage tank 6. When the buffer D performs an extension operation, it is possible to smoothly supply the insufficient hydraulic oil in the cylinder 1 from inside the liquid storage tank 6, and it is expected that a more stable damping force can be further generated.

[0058] In addition, in the above case, a compression-side check valve 12 and an extension-side damping valve 13 are provided on the piston 2, and an extension-side check valve 14 and a compression-side damping valve 16 are provided on the valve housing 8. However, the buffer D can be a single-flow buffer that only has a compression-side port 2b and a compression-side check valve 12 on the piston 2, and only has a suction port 8f and an extension-side check valve 14 on the valve housing 8, and generates a damping force only through the variable damping valve V.

[0059] Furthermore, in the above buffer D, the liquid storage tank 6 and the liquid storage chamber R3 are communicated through the pipe 5. However, as shown by the buffer D1 in a modification of an embodiment in Figure 3 , when a container 6a for forming the liquid storage tank 6 is integrally formed on the outer pipe 4, the pipe 5 can also be omitted, and the liquid chambers L of the liquid storage chamber R3 and the liquid storage tank 6 are communicated through a hole 20 penetrating the outer pipe 4 and the container 6a. Even in the buffer D1 configured in this way, since the liquid storage tank 6 is provided outside the outer pipe 4, the liquid storage chamber R3 can be filled only with hydraulic oil (liquid). When performing an extension operation or a contraction operation, even if the hydraulic oil (liquid) flows into the liquid storage chamber R3 through the variable damping valve V, it is possible to prevent gas from being entrained in the hydraulic oil (liquid) in the liquid storage chamber R3. In addition, even if the inside of the liquid storage tank 6 is not partitioned into gas and liquid by a partitioning member, since the liquid storage chamber R3 is communicated with the liquid storage tank 6 through the hole 20, the flow rate of the hydraulic oil (liquid) is slowed down, and it is also possible to prevent gas from being entrained in the hydraulic oil (liquid) in the liquid storage tank 6. Therefore, according to the buffer D1 configured in this way, since there is no need to worry about gas being entrained in the liquid storage chamber R3, the overall length of the outer pipe 4 can be shortened. Not only can the basic length of the buffer D1 be shortened without deteriorating its mounting performance on the installation object, but also gas can be prevented from being entrained in the hydraulic oil (liquid), so that gas can be prevented from mixing into the cylinder 1, and thus the expected damping force can be exerted.

[0060] The preferred embodiments of the present invention have been described in detail above, but modifications, deformations, and changes can be made as long as they do not depart from the scope of the claims. Symbolic description

[0061] 1 Cylinder 2 Piston 3 Piston rod 4 Outer tube 6 Liquid storage tank 7 Intermediate cylinder D Buffer P Damping channel R1 Extension side chamber R2 Compression side chamber R3 Liquid storage chamber V Variable damping valve.

Claims

1. A buffer, comprising: a cylinder, a piston that is freely movably inserted into the cylinder and divides the interior of the cylinder into an extension side chamber filled with liquid and a compression side chamber, a piston rod inserted into the cylinder and connected to the piston, an outer tube disposed on the outer peripheral side of the cylinder and forming a liquid storage chamber filled only with liquid inside, a damping passage that communicates the extension side chamber with the liquid storage chamber, a variable damping valve provided on the damping passage and capable of adjusting the resistance applied to the liquid flowing from the extension side chamber to the liquid storage chamber, a liquid storage tank disposed outside the outer tube and communicating with the liquid storage chamber for storing liquid.

2. The buffer according to claim 1, wherein the outer tube covers the cylinder over the entire axial length.

3. The buffer according to claim 2, wherein an intermediate cylinder is provided between the cylinder and the outer tube and forms the damping passage therebetween and the cylinder, the liquid storage chamber is formed between the intermediate cylinder and the outer tube.

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